This invention is related to flexographic printing machines of the type which use an ink chamber with doctor blades as a trough to apply aniline ink to a roller. It is particularity related to mechanisms for draining ink from the chamber for cleaning or color change.
An inking trough of this general type, with an automatic washing system, is disclosed in U.S. Pat. No. 3,800,702 (L. Roberts). In machines of the type disclosed in the patent, the ink is drained from the trough or chamber by gravity feed or by mechanical pumping prior to the wash-up cycle. High viscosity ink drains slowly under gravity feed alone. Consequently, pumping is preferred for rapid ink changes, but mechanical pumps accumulate coatings of dried ink and require frequent disassembly and cleaning.
Consequently, an object of this invention is to provide an improved ink evacuation system for the ink chamber which evacuates the ink rapidly, but does not require the evacuated ink to pass through a mechanical pump.